Blue Pinkgill

The Blue Pinkgill (Entoloma hochstetteri) is among the most photographed fungi of the Southern Hemisphere and appears on New Zealand's fifty-dollar note. Its cap is a saturated indigo to sky blue, a pigment that is rare among agarics and that makes the species instantly recognisable in the gloom of a wet podocarp or beech forest.

Despite the colour, it is a fairly typical member of Entoloma, a large genus defined microscopically by angular, pink spores. The pink spore print combined with attached gills separates Entoloma from most other pink-spored groups. In this species the young gills are blue-tinged and only gradually pick up the pink of the maturing spores, so colour changes with age.

The Maori name werewere-kokako refers to the blue wattle of the kokako bird, whose colour the cap matches. The related Entoloma virescens of New Zealand and Japan shares the blue colouring, and there are additional blue Entoloma records from India and elsewhere.

Cap

Small, 1-4 cm across, sharply conical to bell-shaped, usually retaining a distinct pointed umbo even in age. The surface is dry, finely fibrillose to slightly scaly, and coloured deep indigo, ultramarine or greenish-blue, often paler and greyer with age or in dry weather. The margin is thin and may be somewhat grooved.

Gills

Adnate to narrowly adnexed and moderately spaced. Young gills are pale blue to bluish-grey; as spores mature they become suffused with salmon-pink to reddish-pink, giving a two-tone effect in transition. Gill edges are even and concolorous.

Stipe

Slender, 3-7 cm long and 2-6 mm thick, cylindrical, hollow and fragile, coloured the same blue as the cap or slightly paler, with fine longitudinal fibrils. There is no ring and no volva. The base is often clothed in white mycelial down and picks up litter fragments.

Flesh and spore print

Flesh is thin and bluish, without a marked colour change when cut. The spore print is pink, and under the microscope the spores are angular in outline, a defining feature of the genus.

Blue Pinkgill grows in the litter and mossy ground of damp native forest, particularly under southern beech (Nothofagus) and in mixed podocarp-broadleaf forest with a deep, humid, moss-rich floor. It favours shaded stream sides, banks and the edges of tracks where humidity stays high.

It is best known from both main islands of New Zealand, where it fruits from late summer through autumn into early winter, and it has also been reported from India. Fruit bodies occur singly, scattered, or in small loose groups, and are usually noticed against dark leaf litter or green moss.

The ecological role of Entoloma hochstetteri is not fully settled. Many Entoloma species are litter saprophytes, and this one is generally treated as a decomposer of leaf litter and humus in the forest floor. Some members of the genus are known to form associations with plant roots, and a mycorrhizal or partly mycorrhizal lifestyle involving native forest trees has been suggested.

Whatever the exact strategy, the fungus depends on undisturbed, continuously humid native forest floor, which is why it is regarded as an indicator of good-quality remnant forest. The blue pigment is an azulene derivative and is not connected to the spore colour, which comes from the maturing pink spores accumulating on the gills.

Entoloma virescens is the closest match, also blue and conical, but tends to be a paler, greener sky-blue, with a smoother, silkier cap and a more slender build; it is likewise pink-spored. Blue species of Gliophorus and Hygrocybe, such as Gliophorus viridis and other green-blue waxcaps, have thick, waxy, widely spaced, decurrent gills, a slimy cap and stipe, and a white spore print rather than pink.

Small blue-grey Mycena species have white spore prints, more fragile stems and less saturated colour. Leptonia-type entolomas that are dark bluish-grey have scurfy or scaly cap centres, but they lack the intense indigo of the Blue Pinkgill and are usually broader and less sharply conical.